Starting/electrical problem. Solved!

[mr self destruct]

I got back from my holiday Sunday to find the bike dead as a Dodo, so charged up the battery and tested it. Fully charged it was reading 12.8v.


However, I connected it up and ran my multimeter from the earth strap to the -ve terminal, and without even the key in the ignition found 12v flowing.


Fired the engine up first time and it ran a treat, then tried starting it yesterday, and the starter barely spun. Flat as a pancake again, so the evidence pointing to a short somewhere draining the battery.


I put it back on charge this morning, got 12.8v, reconnected it, fired up the bike fine.


Tested the volts at tickover, got 13, took it up to 5,000rpm, got 14.3, which points to it charging ok.


Switched off, put my helmet and gloves on, tried to start it, nothing again! The starter barely moved, the ignition lights faded out, then the starter solenoid did that clicky thing when you have a flat battery. All the signs pointed towards a flat battery again, turning the ignition on but when I tested it it read 12.8 volts! I stuck it on charge again and the charger switched off after 2 minutes because the battery was full of juice.


So what could be causing this? If it's a seized starter motor (I've had that before on my Virago) then the ignition lights would come on bright until I hit the button, but they don't.
It's all the classic signs of a flat battery, without the flat battery.
Could it be the regulator or rectifier? If it was then the voltage between 1500-5000prm wouldn't be stable at 14.3v would it?
Immobiliser maybe, but when they go a bollock they cut everything off?


Any thoughts?

[Paul]

I'm not very good on electrics, but if it were me I'd:


Charge the battery up fully.


Put it on the bike.


Turn the ignition on but not start the bike up


Then I'd turn the lights on to dip or main beam.


Then I'd leave it and see how long it took the battery to go semi flat.


If goes semi flat quite quickly you know you've got a duff battery (exactly how long pretty quickly is I don't know, but it should last longer than say fifteen minutes)


There's probably a simpler way of doing it with a multi-meter but I don't what it is.

[mr self destruct]

Yeah I see where you're coming from, but I don't think it's a duff battery because it takes minutes for the charger to switch off when it's topped up, and the bike takes seconds to run out of juice. It's properly weird.

[Fazerider]

I don't understand how you get 12v between the earth strap and the negative terminal of the battery since they should be connected, even with the ignition off.
Aside from that it's pointing to poor continuity somewhere.  Cleaning and tightening all the connections (battery, fuseholders etc.) will chase away most of these type of faults. I'd agree it looks like the charging side of things is OK.

[Andy FZS]

If the battery reads 12, 8v and it will not start and if I'm reading correctly your lights don't work either then it's going to be a bad connection.  I start with the battery connection.  Also if lights don't work try a bit of wire from -v to a bolt or similar on the engine or frame just to prove the earth strap. Keep posting and I'll keep thinking.

[Ebme Geek]

You may think you have a charged battery, but if it has suffered sulphation (very likely if it has spent much time discharged) it may not be absorbing very much power, so the charger comes upto voltage very quick then goes into float mode (or whatever it does), but no real amount of energy has actually been put into the bettery. And what you see after you take the charger off is just a surface voltage and does not represent the charge in it.
 
Go wit a load test as mentioned by Paul
 
Start with a "charged" battery"    The meter here is not crucial, but it will give a bit more info.
If your meter has a 10 or 20A current range, make sure you have your probes in the right holes on it and connect it in series with your negative terminal ie one attached (black) to the battery neg post and the other (red) attached to the bikes negative lead.   
Now lets add up  headlight 50Watts  2x tail lights 10W  thats 60W or 5amps at 12v  allow a bit for dash lights, guages and ignition and I would guess 5.5 amp
 
Turn it on dip lights see what it draws, a 10amp-hour battery even at HALF it's capacity should be able to keap this up for approx 50 mins, so if yours can't for even 15 mins I would say it is pretty shot
 
How old is battery and how long has it spent flat in it's life ?
 
Or you might find some strange readings
 
Alternately/and/or on lines with Andy, From a charged battery, measure the voltage ( DONT FORGET TO MOVE THE LEAD ON YOUR METER if you moved it before and reselect voltage ) across the battery directly on the terminal posts and then turn dip lights on and see if and how fast the voltage dips/dies and to what voltage
 
Post up results, Ill keep an eye on this as I can but it is sounding typically a sulphated battery not holding much energy

 

[mr self destruct]

Thanks for the replies.
It sounds like I either actually do have a duff battery (it’s two years old by the way) and it’s giving a decent burst of juice the first time then fading out, or it is a connection problem.
[/size]If the latter, I’m thinking a bad earth strap as it stops the lot working rather than just one system.Having said that, what would cause me to see the 12 volts between the disconnected –ve terminal and the earth strap when I hook up the meter? Maybe I should have been checking current instead of voltage?[size=0pt][/size]

[Andy FZS]

Hmmm now err hmm er ok lets see if this makes any sense, if the earth strap was disconnected and you put a volt meter between the battery and earth you would get a reading of 12v ish as the clock etc would make the circuit but due to the high resistance of the meter there would be minimal volt drop on the clock and hence 12v on the meter. It makes sense to me but just sounds like drivel. Maybe someone else can explain better, or when you get the fault put a jump lead from the battery to the frame or just wiggle the connection and see if it helps. I'm trying to help honest but things that are easy in front of me are confusing by post. Good luck. Andy

[Fazerider]

II hadn't twigged that you'd disconnected the negative terminal when you got that 12v reading.
Andy FZS is correct, the speedometer is still powered even when the ignition is off (which is why when you disconnect the battery your tripmeter goes to zero) so that path may have been enough to give you the reading you saw.
Rather than trying to make readings of current (I find it's easy to absent-mindedly short things out that way) I'd stick to the voltage range. Just measure the voltage across the battery while you turn the lights on, if the voltage plummets it's a sulphated battery, if it holds up and the lights don't come on it's loose or dirty connections somewhere.

[mr self destruct]

Ahh of course! Well I've just measured the voltage again and it's 12.8, but with the ignition on it drops to 11, and with the lights on it drops to 3!

Right,  I'm off to get a new battery. 

[Soapy]

I had this issue a little while back. When I got my new battery there was a slip of paper in the box and I was amazed that as little as 0.5 volt down (offload) after a full charge then letting it settle for an hour or so before taking a reading means the battery is only at 50% capacity. I now use an Optimate and when I come home after two weeks I don't have any issues with starting. It does a battery no favours constantly letting it discharge to a low voltage and charging it back up again. One word of warning. Do not go for a constant charger, this will boil your battery dry and buckle the plates ruining your battery.

[Andy FZS]

Sounds like you might be sorted then. Now it's what battery to get. Lol.
Andy

[mr self destruct]

I had this issue a little while back. When I got my new battery there was a slip of paper in the box and I was amazed that as little as 0.5 volt down (offload) after a full charge then letting it settle for an hour or so before taking a reading means the battery is only at 50% capacity. I now use an Optimate and when I come home after two weeks I don't have any issues with starting. It does a battery no favours constantly letting it discharge to a low voltage and charging it back up again. One word of warning. Do not go for a constant charger, this will boil your battery dry and buckle the plates ruining your battery.

I went to my local Yamaha dealer (Alf England) this morning and explained the problem, saying the battery looks almost fully charged and the guy told me pretty much what you've shown here. One volt means the difference between fully charged and knackered. Also that you will get 12v constantly running through, and it's the amps you want to watch.


Anyway, one brand new battery and a nice summer jacket got it sorted.


Thanks a lot for your help guys!